Figure 3-19.-Closed valley flashing.Figure 3-20.-Flashing around a chimney.They can be applied on both roof surfaces at thesame time with each course, in turn, woven overthe valley.Each surface can be covered to the pointapproximately 36 inches from the center of thevalley and the valley shingles woven in placelater.In either case, the first course at the valley is laidalong the eaves of one surface over the valley lining andextended along the adjoining roof surface for a distanceof at least 12 inches. The first course of the adjoiningroof surface is then carried over the valley on top of thepreviously applied shingle. Succeeding courses are thenlaid alternately, weaving the valley shingles over eachother.Figure 3-21.-Step flashing.The shingles are pressed tightly into the valley andnailed in the usual manner. No nail should be locatedcloser than 6 inches to the valley center line, and twonails should be used at the end of each terminal strip.As you approach a chimney, apply the shingles overthe felt up to the chimney face. If 90-pound roll roofingis to be used for flashing, cut wood cant strips and installthem above and at the sides of the chimney (fig. 3-20).The roll roofing flashing should be cut to run 10 inchesup the chimney. Working from the bottom up, fit metalcounterflashing over the base flashing and insert it1 1/2 inches into the mortar joints. Refill the joints withmortar or roofing cement. The counterflashing can alsobe installed when the chimney masonry work is done,Where the roof intersects a vertical wall, it is best toinstall metal flashing shingles. They should be 10 incheslong and 2 inches wider than the exposed face of theregular shingles. The 10-inch length is bent so that it willextend 5 inches over the roof and 5 inches up the wall(see figure 3-21). Apply metal flashing with each3-17
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